In magnetic disk drives, data is written and read by magnetic transducers called “heads.” The magnetic disks are rotated at high speeds, producing a thin layer of air called an air bearing surface (ABS). The read and write heads are supported over the rotating disk by the ABS, where they either induce or detect flux on the magnetic disk, thereby either writing or reading data. Layered thin film structures are typically used in the manufacture of read and write heads. In write heads, thin film structures provide high area density, which is the amount of data stored per unit of disk surface area, and in read heads they provide high resolution.
The present invention is directed generally to devices that can be used, in some implementations, as heads for disk drives, and more particularly the present invention is directed to magnetic tunnel transistors (MTT). A magnetic tunnel transistor (MTT) includes a ferromagnetic emitter, such as cobalt Iron (CoFe), a tunnel barrier, a single ultrathin ferromagnetic base layer, and a collector that heretofore has been made of GaAs.
As recognized herein, the use of GaAs as a collector is not as compatible in read head sensor applications as might be hoped. The present invention understands that preferably, only so-called “hot” electrons, also referred to as “ballistic” electrons, tunnel from the emitter through the base to the collector, because such electrons advantageously do not undesirably scatter. It is thus desirable to preferentially select “hot” electrons and to de-select lower energy electrons. With these recognitions in mind, the invention herein is provided.